1. Field on the Invention
The present invention relates to an electric field emitter tip, for a field emission display (FED) device and more particularly to a high curvature diamond field emitter tip fabrication method.
2. Brief Description of the Conventional Art
Electron emission occurring from a solid facet due to an applied electrical field is a physical property which is utilized for the implementation of electronic displays such as a field emitting display (FED) which is a flat panel type displays, and is implemented as a vacuum microelectronics device. A very basic requirement in such an application is to secure a high quality field emitter capable of emitting electrons when an electrical field is applied. Characteristics required for an improved field emitter include facilitated electron emission, an increased electron emission, and enhanced durability.
Recent studies on electric field emitter development have followed two directions. One proposal involves inducing electron emission by concentrating the electrical field on a tip unit having a geometrically high curvature. The other proposal involves employing as an emitter a material having a low work function value which is essential for electrons to escape from a solid phase.
In the case of the former proposal, a tip having pointed top portions has been formed using materials such as Si and Mo by means of a dry etching process or a specialized deposition, and its electron emission effect has been confirmed and studies are being made as to how to apply the effect to a field emission display, as reported in H. F. Gray, Proc. 29th. Int. Field Emission Symp., 111 (1982), C. A. Spindt, C. E. Holland, A. Rosengreen and I. Brodie, IEEE. Trans. on Electron Devices, 38, 2355(1991).
In the latter proposal, there are reported study results concerning a variety of materials. Among the materials, diamond shows the most promise, because the use of diamond decreases significantly the degradation occurring when used as a field emitter due to its outstanding mechanical, thermal and radiation-proof properties, as well as showing a negative electron affinity, as reported in B. B. Pate, Surf. Science, 165, 83(1986). The negative electron affinity characteristic of diamond provides advantages such as a simplified process in which diamond is formed into a plate type emitter instead of a tip type, and increased durability.
Since diamond has a negative electron affinity characteristic, a diamond formed into a plate shape is still expected to emit electrons therefrom. However, when tips are formed geographically and the electrical field concentration effect is supplemented, increased electron emission under much lower applied voltage can be expected.
Towards such objectives, a variety of trials are being made, one of which, for example is to coat diamond into a film on a Si or Mo tip which has been developed as a conventional field emitter, as reported in N. S. Xu, Y. Tzeng and R. V. Latham, J. Phys. D26, 1776 (1993), V. V. Zhirnov, E. I. Givargizov and P. S. Plenkhanov, J. Vac, Sci. and Tech., B13(2), (1995). However, the fabrication method as tried in the above-described example exhibits disadvantages in that without a special spreading process being performed on the substrate surface prior to diamond deposition, the low density diamond nucleus being deposited therein it remains difficult to achieve uniform diamond film deposition thereon, as reported in A. A. Mosish and P. E. Pehrsson, Appl. Phys. Lett., 59, 417 (1991), and due to Si tip weakness it is also difficult to coat a uniform diamond film on the tips using the conventional spreading processing.
According to S. Yugo, T. Kimura and T. Muto, Vacuum, 41, 1364 (1990), a bias enhanced nucleation method for improving nucleus density by applying within a plasma, a direct voltage to a substrate has been introduced, but still encounters difficulties in forming a tantamount nucleus.
Additionally, according to W. P. Kang, J. L. Davidson, Q. Li, D. L. Kinser and D. V. Kerns, 3rd Int. Conf. on Appl. of Diamond Films and Related Materials, ed. by A. Feldman et al., NIST Washington D.C., p.37 (1995), recent studies on forming a diamond thin film directly into a tip are also being performed, which method includes forming an Si substrate having tip type incisions therein, depositing diamond in the incisions, detaching the Si substrate therefrom, and forming an embossed type diamond tip thereon. The diamond tip formed as described above exhibits a better field emission property compared to that of a plate type diamond film, however, the above-described diamond tip fabrication method shows limits in controlling its curvature, since the diamond tip curvature is controlled by the Si etching degree. Besides, the complicated fabrication process triggers further difficulties in forming a field emitter array.